The invention concerns an apparatus having a radial piston device, in particular, a radial piston pump or motor or the like.
Such radial piston devices, where they have been used in radial piston pumps, for instance, are also used to handle low-viscosity fluids such as brake fluid. In such pumps, the sealing gaps must of necessity be particularly long in order to keep pumping losses low. In this type of pump, this leads to long fluid flow control taps and correspondingly wide pump bodies. The pressure-absorbing conduits in the fluid flow control taps exert a unilateral pressure force on the pump body, a pressure which increases with increasing width of the body. These forces must be compensated for by correspondingly arranged pressure-absorbing zones.
To compensate for these forces, DE-OS 2 236 125 for instance provides pockets molded into the fluid flow control taps in such a fashion that they lie offset to the sides of the control openings and are periodically connected to the cylinder openings in the control taps. DE-OS 22 39 757 also shows pocket-like pressure zones on the output and intake sides; these are diagonally connected and supplied with pressurized fluids through the gap between the pump body and the control tap. Similar arrangements are also to be found in U.S. Pat. No. 3,893,376 and U.S. Pat. No. 3,875,852.
These pocket-like pressure zones have the disadvantage that, even when the pump body is rotated relative to the fluid flow control taps, no appreciable directional fluid movement occurs, so that the pressure in all areas of the chamber is approximately equal, and the force acting on the pump body is the same both in size and direction. This is disadvantageous when, as described above, long control taps produce a one-sided force acting on the pump body which must be met at this point with a increased counter-pressure.